Small size memory card, including xD Picture card, Secure Digital™ (SD) card, SmartMedia™ (SM) card, Multimedia card (MMC), CompactFlash™ (CF) card and PC card are assembled by first making the printed circuit board (PCB) with the contact pads and mounting points for components including microchips (11) such as flash memory, micro-controller, etc. to be mounted thereunto as shown schematically in FIG. 1 (Prior Art). Once the components are mounted, the populated PCB (10) is then fitted into a 2-piece plastic or metal housing (12, 14) which may be snapped fit to close and sealed by microwave or ultrasound leaving certain parts such as the contact pads (16) exposed via openings (18).
In addition to the additional step of assembling the 2-piece housing (12, 14) to sandwich the populated PCB (10) within, the nature of such housing requires certain tolerances which results in minimum gaps or spaces within to allow the PCB to be fitted therein and avoid damaging the components if the 2 parts of the housing are being snapped too hard to fit and close. Such spaces, in turn, enable the assembled card to flex under stress, which may eventually lead to the 2-piece housing to delaminate, crack, separate, and/or solder joints of the components on the PCB to deteriorate or weaken due to the flexing of the PCB.
Another weakness of this conventional construction is the space behind the contact pads, which is also frequently subjected to stress as the card is inserted into a device to be read and removed. Some form of padding or reinforcement is required behind this area to counter the stress, which otherwise may cause the PCB to flex within the housing. Accordingly, the conventional housing provides for a thickening of the area (20) corresponding to the PCB's other side of the contact pads to provide the requisite support. To avoid a resulting weakened or fault line from a rapid fall in thickness of the housing piece, a tapering (22) is usually provided to gradually decrease the thickness which renders an even larger area of the PCT to be unpopulated (24).
The 2-piece housing structure also places a minimal thickness factor on each of the 2 pieces of the housing, thus reducing the internal space, especially thickness, for e.g. increasing memory storage space by increasing the number of memory chips mountable on the PCB. Minimum wall thickness is limited by the high pressure required to fill at a large width-to-thickness ratio, as well as difficulty in removing thin parts from the mould.